I propose to analyze and characterize the large amount of informational RNA present in the mature oocyte of Xenopus laevis laevis and to define its role, if any, in the control of early development and cell differentiation of the embryo. To this end, I will measure the sequence complexity of the poly(A)-containing RNA isolated from Xenopus oocytes, tadpoles, and tissue culture cells. In addition, I will measure the degree to which these cell types contain the same, or different, poly(A)-containing RNA species. I also propose to measure the degree to which all of the oocyte informational RNA is stored in the form of poly(A)-containing RNA. Moreover, I plan to isolate the mRNA species which code for the ribosomal proteins of Xenopus laevis. Bibliographic references: Three abundance classes in HeLa cell messenger RNA. Bishop. J.O., Morton, J.G., Rosbash, M., and Richardson, M. Nature 250, 199-204 (1974): Analysis of the C-Value paradox by molecular hybridization. Rosbash, M., Ford, P. J., and Bishop, J.O. Proc. Natl. Acad. Sci. USA 71, 3746 (1974).